Thermosetting solution composition and prepreg

ABSTRACT

A thermosetting solution composition composed of a biphenyltetracarboxylic acid compound containing a partial lower aliphatic alkyl ester of 2,3,3′,4′-biphenyltetracarboxylic acid and/or a partial lower aliphatic alkyl ester of 2,2′,3,3′-biphenyltetracarboxylic acid, an aromatic diamine compound in a molar amount larger than a molar amount of the biphenyltetracarboxylic acid compound, a partial lower aliphatic aryl ester of 4-(2-phenylethynyl)phthalic acid compound in a molar amount as much as 1.8-2.2 times a molar amount corresponding to a difference between the molar amount of the aromatic diamine compound and the molar amount of the biphenyltetracarboxylic acid compound, and an organic solvent composed of a lower aliphatic alcohol is of value for manufacture of a prepreg.

FIELD OF THE INVENTION

The present invention relates to a thermosetting solution composition, aprepreg utilizing the same, and a method for manufacturing an aromaticpolyimide resin article from the prepreg. In particular, the inventionrelates to a thermosetting solution composition favorably employable formanufacturing a prepreg and further an aromatic polyimide resin article.

BACKGROUND OF THE INVENTION

It is known that an aromatic polyimide resin article shows veryfavorable physical and chemical characteristics such as high mechanicalstrength, high heat resistance, and high resistance to chemicalcompounds. Accordingly, the aromatic polyimide resin has been widelyemployed for manufacturing substrate plates of electronic devices. Thefavorable physical and chemical characteristics of the aromaticpolyimide resin have recently received increased attention, and hencethe aromatic polyimide resin has been studied for the use inmanufacturing various constitutional units of aeroplane and spacecraft.In fact, some aromatic polyimide resin articles are employed in thesetechnical fields.

An aromatic polyimide article such as an aromatic polyimide sheet isgenerally manufactured by first preparing a solution of a polyamic acid(i.e., polyamide acid) by the reaction between an aromatictetracarboxylic acid derivative and an aromatic diamine in a solvent,spreading the polyamic acid solution on a temporary support to prepare apolyamic acid sheet, and finally heating the polyamic acid sheet to givethe polyimide sheet upon drying and cyclization reaction.

An aromatic polyimide article having a large thickness or an aromaticpolyimide article of non-sheet form is generally manufactured utilizinga plurality of prepregs. A plurality of the prepregs are laminated oneon another and then heated under pressure to give an aromatic polyimidearticle. The prepreg is prepared by impregnating a sheet matrix of areinforcing fiber with a thermosetting polymer solution composition.

Japanese PC publication 2002-511902 discloses a method of preparing aprepreg from a polyimide precursor solution which has a solidconcentration of 50 to 80 wt. %, a volatile concentration of not higherthan 35 wt. %, and a Brookfield viscosity of 4,000 to 10,000 cP. Thetypical polyimide precursor solution is prepared from oxydiphthalicdianhydride, phthalic acid and 3,4′-oxydianiline. The solvent of thesolution typically is a mixture of N-methyl-2-pyrrolidone and ethanol.

Japanese Provisional Patent Publication 2000-219741 A describes a terminmodified imide oligomer solution (thermosetting solution composition)which is obtained by the reaction of 2,3,3′,4′-biphenyltetracarboxylicacid with an aromatic diamine compound and 4-(2-phenylethynyl)phthalicanhydride and further describes that the solution composition isemployable for manufacturing a prepreg and further an aromatic polyimidearticle (i.e., cured article). The publication describes a list ofsolvents employable for the preparation of the solution compositionwhich includes N-methyl-2-pyrrolidone, N,N-dimethylformamide,N,N-diethylacetamide, N,N-diethylacetamide, and N-caprolactam.

Japanese Provisional Patent Publication 2004-331801 A describes that2,2′,3,3′-biphenyltetracarboxylic dianhydride is employable for thepreparation of an aromatic polyimide as the aromatic tetracarboxylicacid compound, and further describes that the dianhydride is reactedwith an aromatic diamine compound in the presence of a reactivecrosslinked agent to give a polyamic acid oligomer.

The thermosetting solution composition comprising the terminal modifiedimide oligomer solution prepared by the reaction of2,3,3′,4′-biphenyltetracarboxylic acid with an aromatic diamine compoundand 4-(2-phenylethynyl)phthalic anhydride in a solvent is of value forpreparing an aromatic polyimide article (i.e., cured article) havingexcellent physical and chemical properties. However, all solventsdescribed in the publication as the solvents employable for thepreparation of the imide, that is, N-methyl-2-pyrrolidone,N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylacetamide, andN-caprolactam, have a high boiling point. Therefore, removal of thesolvent from the solution composition by evaporation requires hightemperatures and long periods of time. These evaporation conditions arenot favorable from the viewpoint of industrial preparation.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide athermosetting solution composition which is easily removed bydistillation in the process of preparation of a prepreg for the use ofmanufacture of an aromatic polyimide article (i.e., cured article) andfurther in the process of the manufacture of the cured article andfurther which is easily handled in the industrial process.

It is another object of the invention to provide a prepreg which isfavorably employable for manufacture of an aromatic polyimide article(i.e., cured article) by way of heating under pressure from theviewpoints that the solvent used as well as water and alcohol which areby-produced in these processes are easily removed by evaporation.

The inventors of the present invention have noted and studied thethermosetting solution composition described in Japanese ProvisionalPatent Publication 2000-219741 A. As a result of the studies, they havediscovered that when 2,3,3′,4′-biphenyltetracarboxylic dianhydride and4-(2-phenylethynyl)phthalic anhydride are dissolved in a lower aliphaticalcohol such as methanol or ethanol and heated, a partial loweraliphatic alkyl ester of 2,3,3′,4′-biphenyltetracarboxylic acid and apartial lower aliphatic alkyl ester of 4-(2-phenylethynyl)phthalic acidboth of which are soluble in the employed alcohol are produced, and thata solution composition comprising the resulting solution and an aromaticdiamine compound shows a stable solution viscosity. The inventors havefurther discovered that the resulting solution composition is favorablyemployable for preparing a prepreg and furthermore that the prepreg iseasily converted into a cured polyimide article. The lower aliphaticalcohol employed as a solvent of the thermosetting solution position isadvantageous in that its boiling point is low, that it is easily removedby evaporation, that it is easily handled, and that the cost is low.Accordingly, the use of the lower aliphatic alcohol as the solvent ofthe thermosetting solution composition is very advantageous particularlyfrom the viewpoint of the industrial preparation of the thermosettingsolution composition and the prepreg.

The present invention resides in a thermosetting solution compositioncomprising a biphenyltetracarboxylic acid compound containing at least15 mol % of a partial lower aliphatic alkyl ester of2,3,3′,4′-biphenyltetracarboxylic acid and/or a partial lower aliphaticalkyl ester of 2,2′,3,3′-biphenyltetracarboxylic acid, an aromaticdiamine compound in a molar amount larger than a molar amount of thebiphenyltetracarboxylic acid compound, a partial lower aliphatic alkylester of 4-(2-phenylethynyl)phthalic acid compound in a molar amount asmuch as 1.8-2.2 times a molar amount corresponding to a differencebetween the molar amount of the aromatic diamine compound and the molaramount of the biphenyltetracarboxylic acid compound, and an organicsolvent comprising a lower aliphatic alcohol.

The lower aliphatic alcohol employed in the invention includes amononalent aliphatic alcohol having 1 to 6 carbon atoms. Therepresentative examples of the lower aliphatic alcohols include methanoland ethanol. The lower aliphatic alkyl ester include an ester with amonovalent aliphatic alkyl alcohol having 1 to 6 carbon atoms. Therepresentative examples include methyl ester and ethyl ester. Thepartial lower aliphatic alkyl ester means that one to three carboxylgroups (generally two carboxyl groups) of the biphenyltetracarboxylicacid form ester bondings with the lower aliphatic alcohol, and that onecarboxyl group of 4-(2-phenylethynyl)phthalic acid forms an esterbonding with the lower aliphatic alcohol.

The present invention further resides in a thermosetting solutioncomposition comprising a biphenyltetracarboxylic acid compoundcontaining at least 15 mol % of a partial methyl ester of2,3,3′,4′-biphenyltetracarboxylic acid and/or a partial methyl ester of2,2′,3,3′-biphenyltetracarboxlic acid, an aromatic diamine compound in amolar amount larger a molar amount of the biphenyltetracarboxylic acidcompound, a partial methyl ester of 4-(2-phenylethynyl)phthalic acidcompound in a molar amount as much as 1.8-2.2 times a molar amountcorresponding to a difference between the molar amount of the aromaticdiamine compound and the molar amount of the biphenyltetracarboxylicacid compound, and an organic solvent comprising ethanol.

The preferred embodiments of the thermosetting solution compositions ofthe invention are set forth below.

-   (1) The lower aliphatic alcohol is methanol, ethanol, or a mixture    of these alcohols.-   (2) The lower aliphatic alkyl ester is methyl ester, ethyl ester, or    a mixture of methyl ester and ethyl ester.-   (3) The molar amount of the partial lower aliphatic alkyl ester of    4-(2-phenylethynyl)phthalic acid compound is as much as 1.95-2.05    times a molar amount corresponding to the difference the molar    amount of the aromatic diamine compound and the molar amount of the    biphenyltetracarboxylic acid compound.-   (4) A total amount of the biphenyltetracarboxylic acid compound, the    aromatic diamine compound, and 2-(2-phenyl-ethynyl)phthalic acid    compound is in the range of 30 to 80 wt. %, per the amount of the    solution composition.-   (5) The biphenyltetracarboxylic acid compound comprises at least 50    molar % of 2,3,3′,4′-biphenyltetracarboxylic acid compound    comprising a partial lower aliphatic akyl ester of    2,3,3′,4′-biphenyltetracarboxylic acid compound.-   (6) The aromatic diamine compound comprises at least 50 molar % of    an aromatic diamine having one aromatic ring in a molecular    structure thereof.-   (7) The aromatic diamine compound comprises p-phenylenediamine,    1,3-bis(4-aminophenyl)benzene, or a mixture thereof.-   (8) An imidazole compound is contained.

The present invention furthermore resides in a thermosetting powdercomposition comprising a biphenyltetracarboxylic acid compoundcontaining at least 15 mol % of a partial lower aliphatic alkyl ester of2,3,3′,4′-biphenyltetracarboxylic acid and/or a partial lower aliphaticalkyl ester of 2,2′,3,3′-biphenyltetracarboxylic acid, an aromaticdiamine compound in a molar amount larger than a molar amount of thebiphenyltetracarboxylic acid compound, and a partial lower aliphaticalkyl ester of 4-(2-phenylethynyl)phthalic acid compound in a molaramount as much as 1.8-2.2 times a molar amount corresponding to adifference between the molar amount of the aromatic diamine compound andthe molar amount of the biphenyltetracarboxylic acid compound.

In the above-mentioned thermosetting powder composition, the partiallower alkyl ester preferably is a partial methyl ester.

The present invention furthermore resides in a prepreg comprising asheet matrix of a reinforcing fiber impregnated with the thermosettingsolution composition of the invention.

The present invention furthermore resides in a method of manufacturing aresin article which comprises laminating a plural number of the prepregsof the invention one on another and heating the resulting laminate underpressure.

The thermosetting solution composition of the invention shows a highsolution stability regardless of using an easily volatile solvent.Therefore, the solvent is easily removed by evaporation and easilyhandled when a prepreg is prepared using the solution composition. Inother words, since the lower aliphatic alcohol employed as the solventhas a low boiling point, removal of the solvent as well as theby-produced water and compounds are easily removed by distillation inthe procedures of the prepreg and the cured polyimide article.

Particularly, when the acid components of the thermosetting solutioncomposition are in the form of methyl esters, the resulting prepregeasily gives a cured polyimide article having a desired form because theprepreg prepared using the thermosetting solution composition comprisingthe methyl esters is hardly deformed in its preparing procedure andshows good moldability.

In addition, when the solvent of the thermosetting solution compositionis ethanol, the environmental atmosphere formed in the process ofpreparing the prepreg and further in the process of the cured polyimidearticle less worsen, as compared with the use of methanol as thesolvent. Accordingly, it is most preferred that the acid components ofthe thermosetting solution composition are in the form of methyl estersand further that the solvent is ethanol.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a graph showing results of dynamic viscoelasticitymeasurements (indicating relationships between temperature and complexviscosity).

FIG. 2 is ¹H-NMR spectrum of the thermosetting solution composition ofExample 10(1).

FIG. 3 is ¹H-NMR spectrum of the thermosetting solution composition ofExample 15(1).

FIG. 4 illustrates an example for the procedure of manufacturing a curedarticle from a prepreg.

FIG. 5 illustrates a phased heating pattern employed in the procedure ofmanufacturing a cured article from a prepreg under vacuum which isperformed varying the heating temperature and the degree of vacuum.

FIG. 6 illustrates a phased vacuum pattern employed in the procedure ofmanufacturing a cured article from a prepreg under vacuum which isperformed varying the heating temperature and the degree of vacuum.

FIG. 7 illustrates a phased pressure pattern employed in the procedureof manufacturing a cured article from a prepreg under vacuum which isperformed varying the heating temperature and the degree of vacuum.

FIG. 8 illustrates another phased heating pattern employed in theprocedure of manufacturing a cured article from a prepreg under vacuumwhich is performed varying the heating temperature and the degree ofvacuum.

FIG. 9 illustrates another phased vacuum pattern employed in theprocedure of manufacturing a cured article from a prepreg under vacuumwhich is performed varying the heating temperature and the degree ofvacuum.

FIG. 10 illustrates another phased pressure pattern employed in theprocedure of manufacturing a cured article from a prepreg under vacuumwhich is performed varying the heating temperature and the degree ofvacuum.

DETAILED DESCRIPTION OF THE INVENTION

The monomer compounds required for the preparation of the thermosettingsolution composition of the invention are described below:

(1) a biphenyltetracarboxylic acid compound containing at least 15 mol %of a partial lower aliphatic alkyl ester of2,3,3′,4′-biphenyltetracarboxylic acid and/or a partial lower aliphaticalkyl ester of 2,2′,3,3′-biphenyltetracarboxylic acid;

(2) an aromatic diamine compound in a molar amount larger than a molaramount of the biphenyltetracarboxylic acid compound; and

(3) a partial lower aliphatic alkyl ester of 4-(2-phenylethynyl)phthalicacid compound (a portion less than 50 molar % may be not in the form ofthe alkyl ester) in a molar amount as much as 1.8-2.2 times a molaramount corresponding to a difference between the molar amount of thearomatic diamine compound and the molar amount of thebiphenyltetracarboxylic acid compound.

The biphenyltetracarboxylic acid compound contains at least 15 molar %(preferably, at least 30 molar %, more preferably, at least 50 molar %,most preferably at least 80 molar %) of a partial aliphatic alkyl esterof 2,3,3′,4′-biphenyltetracarboxylic acid and/or a partial aliphaticalkyl ester of 2,2′,3,3′-biphenyltetracarboxylic acid. More preferably,the biphenyltetracarboxylic acid compound comprises a partial aliphaticalkyl ester of 2,3,3′,4′-biphenyltetracarboxylic acid.

The partial aliphatic alkyl ester of 2,3,3′,4′-biphenyltetracarboxylicacid can be prepared by placing 2,3,3′,4′-biphenyltetracarboxylicdianhydride in a lower aliphatic alcohol and heating the resultingmixture to give a solution. The heating is preferably carried out at atemperature from 40° C. to the boiling temperature of the alcohol, underrefluxing. The 2,3,3′,4′-biphenyltetracarboxylic dianhydride is known asthe starting compound for the preparation of an aromatic polyimideresin. The partial aliphatic alkyl ester of2,2′,3,3′-biphenyltetracarboxylic acid can be prepared by placing2,2′,3,3′-biphenyltetracarboxylic dianhydride in a lower aliphaticalcohol and heating the resulting mixture to give a solution. The2,2′,3,3′-biphenyltetracarboxylic dianhydride is described in detail inthe aforementioned Japanese Provisional Patent Publication 2004-331801A.

In the thermosetting solution composition, a portion (not more than 10molar %) of the partial lower aliphatic alkyl ester of2,3,3′,4′-biphenyltetracarboxylic acid and/or a portion (not more than10 molar %) of the partial lower aliphatic alkyl ester of2,2′,3,3′-biphenyltetracarboxylic acid can be replaced with a partiallower aliphatic alkyl ester of other tetracarboxylic acid. Examples ofthe partial lower aliphatic alkyl esters of other tetracarboxylic acidsinclude a partial lower aliphatic alkyl ester of3,3′,4,4′-biphenyltetracarboxylic acid compound, a partial loweraliphatic alkyl ester of 3,3′,4,4′-benzophenonetracarboxylic acidcompound, a partial lower aliphatic alkyl ester of pyromellitic acidcompound, and a partial lower aliphatic alkyl ester ofbis(3,4-dicarboxydiphenyl)ether.

Examples of the aromatic diamine compounds include p-phenylene diamine,m-phenylene diamine, 1,3-bis(4-aminophenoxy)benzene, and their mixtures.Also employable are aromatic diamine compounds that are known to beutilized for the preparation of aromatic polyimide resins. Thesearomatic diamine compound are described in detail in the aforementionedJapanese Provisional Patent Publication 2000-219741 A. Most preferredaromatic diamine compounds are p-phenylene diamine and aromatic ofp-phenylene diamine and 1,3-bis(4-amiphenyl)benzene, which areadvantageous in preparing a thermosetting solution composition film ofgood form stability.

The aromatic diamine compounds are employed in a molar amount largerthan a molar amount of the biphenyltetracarboxylic acid cow. Forinstance, the aromatic diamine compound is employed 1.1 to 2.0 mols,preferably 1.15 to 1.30 mols, per one mole of thebiphenyltetracarboxylic acid compound.

When a mixture of p-phenylene diamine and 1,3-bis(4-aminophenoxy)benzeneis used as the aromatic diamine compound, the mixture is preferably usedin an amount of 1.15 to 1.30 mols per one mole of thebiphenyltetracarboxylic acid compound, and p-phenylene diamine ispreferably used in an amount of 50 to 70 molar % per the total amount ofthe p-phenylene diamine and 1,3-bis(4-aminophenoxy)benzene, so that theresulting cured polyimide article can have enough heat resistance andgood molding characteristics.

The thermosetting solution composition of the invention furthercomprises a partial lower aliphatic alkyl ester of4-(2-phenylethynyl)phthalic acid in a molar amount as much as 1.8-2.2times, preferably as much as 1.95-2.05 times, a molar amountcorresponding to a difference between the molar amount of the aromaticdiamine compound and the molar amount of the biphenyltetracarboxylicacid compound.

The thermosetting solution composition of the invention furthercomprises an organic solvent comprising a lower aliphatic alcohol(monovalent aliphatic alcohol having 1 to 6 carbon atoms) as a maincomponent. Preferred are methanol and ethanol. A mixture of loweraliphatic alcohols can be employed. However, if the mixture is used, themixture contains preferably at least 50 vol. %, more preferably at least80 vol. %, of methanol or ethanol. Other low boiling point solvents arealso employable in combination with the lower aliphatic alcohol.However, the other lower boiling point solvents in the combinationpreferably is in an amount of 30 vol. % or less.

The thermosetting solution composition of the invention can be easilyprepared by the step comprising the following thee steps:

(1) placing a biphenyltetracarboxylic acid compound containing at least15 molar % of 2,3,3′,4′-biphenyltetracarboxylic dianhydride and/or2,2′,3′-biphenyltetracarboxylic dianhydride, and 4-(2-phenylethynyl)phthalic dianhydride in an organic solvent comprising a lower aliphaticalcohol, to give a suspension;

(2) heating the suspension to give a solution in which a lower aliphaticalkyl ester of the biphenyltetracarboxylic acid c and a lower aliphaticalkyl ester of 4-(2-phenylethynyl)phthalic acid are dissolved;

and

(3) mixing an amotic diamine compound with the solution obtained in (2)above.

It has been noted that a thermosetting solution composition comprisesmethyl esters of the biphenyltetracarboxylic acid compound and4-(2-phenylethynyl)-phthalic acid, a prepreg prepared from the solutioncomposition shows good form stability in the procedure of manufacturinga cured polyimide article under pressure at a high temperature.Accordingly, the lower aliphatic alkyl esters in the thermosettingsolution composition preferably are methyl esters. However, ifenvironmental pollution caused by evaporation of methanol in themanufacture of an aromatic polyimide article from the prepreg should beobviated, the free methanol can be removed from the prepreg by thefollowing method:

preparing first a thermosetting solution composition using methanol;

drying the prepared thermosetting methanol solution composition to givea thermosetting powdery composition;

dissolving the thermosetting powdery composition in ethanol, to give athermosetting ethanol solution composition; and

preparing a prepreg from the thermosetting ethanol solution composition.

In the above-mentioned method, the thermosetting powdery composition ispreferably prepared by heating the thermosetting methanol solutioncomposition to a temperature of not higher than 60° C. The thermosettingpowdery composition may contain a small amount of methanol.

The prepreg preferably contains a volatile component including a loweraliphatic alcohol in an amount of 18 to 25 wt. %, more preferably in anamount of 20 to 22 wt. %.

The thermosetting solution composition of the invention preferablyfurther contains an imidazole compound in an amount of 0.01 to 3 wt. %,per the total amount of the reactive compounds (i.e.,biphenyltetracarboxylic acid compound, 4-(2-phenylethynyl)phthalic acidcompound, and aromatic diamine compound). In the preparation of thethermosetting solution composition, the imidazole compound serves toaccelerate the dissolution of the placed acid components so that thedissolution can be complete within a shortened period of time. Further,the imidazole compound serves to accelerate thermosetting of the prepregin the procedure that the prepreg is heated under pressure tomanufacture a cured polyimide article. There are no specific limitationwith respect to imidazole compounds. Examples of the imidazole compoundsinclude known imidazole catalysts such as 2-methylimidazole and1,2-dimethylimidazole.

In the thermosetting solution composition of the invention, the totalamount of the aforementioned reactive compounds (i.e.,biphenyltetracarboxylic acid compound, 4-(2-phenylethynyl)phthalic acidcompound, and aromatic diamine compound) preferably is 30 to 80 wt. %,more preferably 35 to 75 wt. %, more preferably 40 to 75 wt. %, mostpreferably 45 to 75 wt. %.

A prepreg is prepared by impregnating a matrix sheet of high strengthfibers with the thermosetting solution composition of the invention andheating the impregnated matrix sheet for removing a portion of thesolvent by evaporation.

The prepreg should contain an appropriate amount of a volatile componentand an appropriate amount of a resin component so that it can be easilyhandled for the manufacture of the cured polyimide article. The handlingcharacteristics include drapeability and tackiness. Accordingly, thematrix sheet can be impregnated with the thermosetting solutioncomposition by dip method or cast method, and then heated in a dry airoven to remove an excessive volatile component, so as to prepare anappropriate prepreg having a resin content (Rc) of 35 to 55 wt. % and avolatile content (Vc) of 10 to 25 wt. %. The heating procedure isgenerally carried out at a temperature in the range of 40 to 150° C.,for 0.5 to 30 min.

The matrix sheet comprises known high strength fibers such as carbonfibers, aramide fibers, glass fibers, and ceramic fibers such astitanium dioxide fibers.

The prepreg of the invention can be heated to give a cured polyimidearticle having Tg of higher than 300° C. (or showing no Tg attemperatures of 300° C. or lower).

The prepreg preferably is in the form of a roll and is preferably coatedon both surfaces with a covering sheet such as polyethyleneterephthalate sheet and paper sheet for its storage and transportation.

The prepreg can be processed to give a cured resin article by a varietyof known methods. For instance, a roll of prepreg is cut to give pluralsheets having the desired size. The plural prepreg sheets (for instance,from several sheets to sheets of more than a hundred) are laminated oneon another, and the formed prepreg laminate is heated under pressure bymeans of a hot press. In the procedure of heating under pressure, thethermosetting composition gives an aromatic polyimide article throughthermal imidation reaction and curing reaction.

For instance, the laminate of prepregs is heated under pressure in themanner as illustrated in FIG. 4. In more detail, the laminate ofprepregs 11 are placed between a pair of air permeable sheets (such aspolyethylene terephthalate sheets and glass sheets) 12 a,12 b. On eachof the air permeable sheets 12 a,12 b is placed a release film 13 a,13b. Thus prepared laminate is placed between a pair of heat-resistantnon-woven cloths (sponge materials) 14 a,14 b, and then is encase in aheat-resistant bag 15. The heat-resistant bag 15 is then sealed at theopen end 16, for instance, by heat sealing. The inner space of the bag15 is evacuated by withdrawing air through the evacuation pipe 17 byvacuum pump, while the enclosed laminate is heated under pressure. Inthe procedure of evacuation and heating under pressure, it is preferredto vary the degree of vacuum and temperature according the patternsillustrated in FIGS. 5 to 10.

The present invention is further described by the following non-limitingexamples.

In the following examples, the measured values and calculated values areobtained in the following manners.

-   (1) Total reactive component content in solution    Total reactive component content (%)100×[amounts(g) of the employed    reactive components]/[amounts(g) of the employed reactive    components+amount (g) of the solvent]-   (2) Solution viscosity

The solution viscosity was determined at 25+ C. by means of an E-typeviscometer (available from Tokyo Measuring aratus Co., Ltd.).

-   (3). Glass transition temperature (Tg) of cured resin article

For the measurement, the cured resin article is heated in a nitrogen gasby means of SSC5200-DSC-3200 (available from Seiko-Instrument Co., Ltd.)at a temperature elevation rate of 200° C./min.

-   (4) Linear expansion coefficient of cured resin article

For the measurement, the cured resin article is heated from 50° C. to250° C. in a nitrogen gas by means of TM-50 (available from ShimazuSeisa)s Co., Ltd.) at a temperature elevation rate of 5° C./min.

-   (5) Volatile content (Vc) and Resin content (Rc)    Vc(%)=100×[amount (g) of uncured prepreg−amount (g) of prepreg after    heating at 370° C. for one hour]/[amount (g) of uncured prepreg]    Rc(%)=100×[amount(g) of prepreg after heating at 370° C. for one    hour−amount(g) of matrix sheet]/[amount(g) of prepreg after heating    at 370° C. for one hour]-   (6) Complex viscosity of prepreg

A dynamic viscoelasticity is measured in a nitrogen atmosphere by meansof a melt dynamic viscoelastometer (available from T. A. InstrumentJapan Co., Ltd.) at a temperature elevation rate of 2° C./min.

-   (7) Thermal decomposition temperature of resin article

The heat treated resin article is heated in TG/DTA 6300 (available fromS. I. I. Nanotechnology Co., Ltd) at a temperature elevation rate of 5°C./min. The temperature at which a weight loss of 5 wt. % is observed isrecorded as the thermal decomposition temperature.

-   (8) Measurement of ¹H-NMR spectrum

The ¹H-NMR spectrum was measured at a resonance frequency of 400 MHz ina deuterated methanol by means of a nuclear magnetic spectrometer EX-400type, FT-NMR (available from JEOL, Ltd.).

In the following examples, the following matter components (i.e.,reactive components) were employed:

a-BPDA: 2,3,3′,4′-biphenyltetracarboxylic dianhydride

s-BPMA: 3,3′,4,4′-biphenyltetracarboxylic dianhydride

PEPA: 4-(phenylethynyl)phthalic anhydride

TPE-R: 1,3-bis(4-aminophenoxy)benzene

PPD: p-phenylene diamine

m-phenylene diamine

EXAMPLE 1

(1) Preparation of Thermosetting Solution Composition

In a four-necked 100 mL volume separable flask equipped with a stirrer,a reflux condenser and a nitrogen gas inlet were placed 11.77 g (0.0400mol) of a-BPDA, 4.97 g (0.0200 mol) of PEPA, and 13.54 g of ethanol in anitrogen gas stream. The resulting mixture was stirred under reflux for5 hours to give a homogeneous solution. The solution was then cooled toroom temperature. To the solution were added under stirring 6.58 g(0.0225 mol) of TPE-R and 2.97 g (0.0275 mol) of PPD. The resultingmixture was heated at 60° C. for 60 mixtures to give a homogeneoussolution (thermosetting solution composition).

The homogeneous solution was spread over a polyamide film (Upilex 125S,available from Ube Industries, Ltd.) and successively heated at 80° C.for 30 min., 135° C. for 30 min., 180° C. for 30 min., 250° C. for 30min., 300° C. for 30 muin., and 370° C. for 60 min., to give a clearresin film having a thickness of approx. 0.1 mm.

The viscosity of the homogeneous solution and Tg of the resin film areset forth in Table 1.

(2) Preparation of Prepreg

The above-mentioned homogeneous solution (thermosetting solutioncomposition) was spread over a polyethylene terephthalate (PET) film toform a solution film. On the solution film was placed a carbon fibercloth (FAW 198 g/m², plain cloth, T300-3K, available from Toray Corp.)having a size of 80 mm×100 mm. Thus prepared laminate was placed on ahot plate heated to 40° C. under the condition that the PET film wasbrought into contact with the hot plate. On the hot plate, the uppersurface of the carbon fiber cloth was lightly pressed onto the PET filmso that the cloth could be impregnated with the solution. Subsequently,the solution-impregnated carbon cloth was separated from the PET film,and dried by hanging it for 3 minutes in a hot air oven heated to 100°C. The dry carbon cloth was taken out of the oven, placed between a pairof PET film (thickness: 25 μm), and pressed at a pressure of 0.1 MPa forone minute by means of a hot press heated to 80° C. Thus, a prepreg wasprepared.

(3) Manufacture of Cured Resin Sheet

The prepreg was successively heated at 135° C. for 30 min., 180° C. for30 min., 250° C. for 30 min., 300° C. for 30 min., and 370° C. for 60min., to manufacture a cured resin sheet.

The volatile content (Vc) and resin content (Rc) were determined fromthe data measured in the procedure of manufacturing the cured resinsheet from the prepreg. The determined Vc and Rc are set forth in Table2.

EXAMPLE 2

(1) Preparation of Thermosetting Solution Composition

The procedures of Example 1-(1) were repeated except that the TPE-R, PPDand ethanol were used in amounts of 4.39 g (0.0150 mol), 3.78 g (0.0350mol), and 11.72 g, respectively, to give a homogeneous solution(thermosetting solution composition). Further, the homogeneous solutionwas processed in the same manner as in Example 1-(1), to give a clearresin film (thickness: approx. 0.1 mm).

The viscosity of the homogeneous solution and Tg of the resin film areset forth in Table 1.

(2) Preparation of Prepreg

The procedures of Example 1-(2) were repeated using the homogeneoussolution prepared in (1) above, to prepare a prepreg.

The prepreg was subjected to measurement of dynamic viscoelasticity. Themeasured viscoelasticity is shown in FIG. 1.

(3) Manufacture of Cured Resin Sheet

The procedures of Example 1-(3) were repeated using the prepreg preparedin (2) above, to manufacture a cured resin sheet.

The volatile content (Vc) and resin content (Rc) were determined fromthe data measured in the procedure of manufacturing the cured resinsheet from the prepreg. The determined Vc and Rc are set forth in Table2.

EXAMPLE 3

(1) Preparation of Thermosetting Solution Composition

The procedures of Example 1-(1) were repeated except that the a-BPDA,s-BPDA, PEPA and ethanol were used in amounts of 5.89 g (0.0200 mol),5.89 g (0.0200 mol), 4.97 g (0.0200 mol), and 12.37 g, respectively, togive a homogeneous solution (thermosetting solution composition).Further, the homogeneous solution was processed in the same manner as inExample 1-(1), to give a clear resin film (thickness: approx. 0.1 mm).

The viscosity of the homogeneous solution and Tg of the resin film areset forth in Table 1.

(2) Preparation of Prepreg

The procedures of Example 1-(2) were repeated using the homogeneoussolution prepared in (1) above, to prepare a prepreg.

(3) Manufacture of Cured Resin Sheet

The procedures of Example 1-(3) were repeated using the prepreg preparedin (2) above, to manufacture a cured resin sheet.

The volatile content (Vc) and resin content (Rc) were determined fromthe data measured in the procedure of manufacturing the cured resinsheet from the prepreg. The determined Vc and Rc are set forth in Table2.

EXAMPLE 4

(1) Preparation of Thermosetting Solution Composition

The procedures of Example 1-(1) were repeated except that the a-BPDA,s-BPnM, PEPA and ethanol were used in amounts of 3.53 g (0.0120 mol),8.24 g (0.0280 mol), 4.97 g (0.0200 mol), and 11.27 g, respectively, togive a homogeneous solution (thermosetting solution composition).Further, the homogeneous solution was processed in the same manner as inExample 1-(1), to give a clear resin film (thickness: approx. 0.1 mm).

The viscosity of the homogeneous solution and Tg of the resin film areset forth in Table 1.

(2) Preparation of Prepreg

The procedures of Example 1-(2) were repeated using the homogeneoussolution prepared in (1) above, to prepare a prepreg.

(3) Manufacture of Cured Resin Sheet

The procedures of Example 1-(3) were repeated using the prepreg preparedin (2) above, to manufacture a cured resin sheet.

The volatile content (Vc) and resin content (Rc) were determined fromthe data measured in the procedure of manufacturing the cured resinsheet from the prepreg. The determined Vc and Rc are set forth in Table2.

EXAMPLE 5

(1) Preparation of Thermosetting Solution Composition

The procedures of Example 1-(1) were repeated except that the TPE-R, MPD(in place of PPD) and ethanol were used in amounts of 2.07 g (0.0070mol), 4.66 g (0.0430 mol) and 12.64 g, respectively, to give ahomogeneous solution (thermosetting solution composition). Further, thehomogeneous solution was processed in the same manner as in Example1-(1), to give a clear resin film (thickness: approx. 0.1 mm).

The viscosity of the homogeneous solution and Tg of the resin film areset forth in Table 1.

(2) Preparation of Prepreg

The procedures of Example 1-(2) were repeated using the homogeneoussolution prepared in (1) above, to prepare a prepreg.

(3) Manufacture of Cured Resin Sheet

The procedures of Example 1-(3) were repeated using the prepreg preparedin (2) above, to manufacture a cured resin sheet.

The volatile content (Vc) and resin content (Rc) were determined fromthe data measured in the procedure of manufacturing the cured resinsheet from the prepreg. The determined Vc and Rc are set forth in Table2.

In this example, the following cured resin sheet was furthermanufactured.

(4) Manufacture of Cured Resin Sheet

A carbon fiber cloth (FAW 198 g/m², plain cloth, T300-3K, available fromToray Corp.) was placed in a dry air oven parged with a nitrogen gas,and heated at 350° C. for 30 minutes. By measuring the weight loss ofthe carbon fiber cloth after the heat treatment, it was confirmed that0.7 wt. % of a sizing agent was removed.

The procedures of Example 5-(2) and 5-(3) were repeated using the heattreated carbon fiber cloth and the homogeneous solution of Example5-(1), to prepare a prepreg and then manufacture a cured resin sheet.

The volatile content (Vc) and resin content (Rc) were determined fromthe data measured in the procedure of manufacturing the cured resinsheet from the prepreg. The determined Vc was 15 wt. % and Rc was 39 wt.%.

(5) Manufacture of Cured Resin Sheet

The procedures of Example 5-(2) and 5-(3) were repeated using Tiranofiber cloth (titanium dioxide fiber cloth, FAW 328 g/m², plain cloth,PM-S17E08PX, available from Ube Industries, Ltd.) and the homogeneoussolution of Example 5-(1), to prepare a prepreg and then manufacture acured resin sheet.

The volatile content (Vc) and resin content (Rc) were determined fromthe data measured in the procedure of manufacturing the cured resinsheet from the prepreg. The determined Vc was 16 wt. % and Rc was 39 wt.%.

(6) Manufacture of Cured Resin Sheet

Ten g (10 g) of the homogeneous solution prepared in Example 5-(1) wasdiluted with 2.5 g of methyl ethyl ketone. The resulting solution was ahomogeneous solution.

The procedures of Example 5-(2) and 5-(3) were repeated using theabove-mentioned homogeneous solution, to prepare a prepreg and thenmanufacture a cured resin sheet.

The volatile content (Vc) and resin content (Rc) were determined fromthe data measured in the procedure of manufacturing the cured resinsheet from the prepreg. The determined Vc was 15 wt. % and Rc was 39 wt.%.

EXAMPLE 6

(1) Preparation of Thermosetting Solution Composition

The procedures of Example 1-(1) were repeated using 11.06 g (0.0376 mol)of a-BPDA, 16.55 g (0.0667 mol) of PEPA, 10.38 g (0.0355 mol) of TPE-R,3.84 g (0.0355 mol) of MPD, and 17.09 g of ethanol, to give ahomogeneous solution (thermosetting solution composition). Further, thehomogeneous solution was processed in the same manner as in Example1-(1), to give a clear resin film (thickness: approx. 0.1 mm).

The viscosity of the homogeneous solution and Tg of the resin film areset forth in Table 1.

(2) Preparation of Prepreg

The procedures of Example 1-(2) were repeated using the homogeneoussolution prepared in (1) above, to prepare a prepreg.

(3) Manufacture of Cured Resin Sheet

The procedures of Example 1-(3) were repeated using the prepreg preparedin (2) above, to manufacture a cured resin sheet.

The volatile content (Vc) and resin content (Rc) were determined fromthe data measured in the procedure of manufacturing the cured resinsheet from the prepreg. The determined Vc and Rc are set forth in Table2.

EXAMPLE 7

(1) Preparation of Thermosetting Solution Composition

The procedures of Example 1-(1) were repeated using 15.59 g (0.0530 mol)of a-BPDA, 23.33 g (0.0940 mol) of PEPA, 14.62 g (0.0500 mol) of TPE-R,2.70 g (0.0250 mol) of PPD, 2.70 g (0.0250 mol) of MED, and 25.26 g ofethanol, to give a homogeneous solution (thermosetting solutioncomposition). Further, the homogeneous solution was processed in thesame manner as in Example 1-(1), to give a clear resin film (thickness:approx. 0.1 mm).

The viscosity of the homogeneous solution and Tg of the resin film areset forth in Table 1.

(2) Preparation of Prepreg

The procedures of Example 1-(2) were repeated using the homogeneoussolution prepared in (1) above, to prepare a prepreg.

(3) Manufacture of Cured Resin Sheet

The procedures of Example 1-(3) were repeated using the prepreg preparedin (2) above, to manufacture a cured resin sheet.

The volatile content (Vc) and resin content (Rc) were determined fromthe data measured in the procedure of manufacturing the cured resinsheet from the prepreg. The determined Vc and Rc are set forth in Table2.

EXAMPLE 8

(1) Preparation of Thermosetting Solution Composition

The procedures of Example 1-(1) were repeated except that TPE-R was notused, and that the PPD and ethanol were used in amounts of 5.41 g(0.0500 mol) and 14.46 g, respectively, to give a homogeneous solution(thermosetting solution composition). Further, the homogeneous solutionwas processed in the same manner as in Example 1-(1), to give a clearresin film (thickness: approx. 0.1 mm).

The viscosity of the homogeneous solution and Tg of the resin film areset forth in Table 1.

(2) Preparation of Prepreg

The procedures of Example 1-(2) were repeated using the homogeneoussolution prepared in (1) above, to prepare a prepreg.

(3) Manufacture of Cured Resin Sheet

The procedures of Example 1-(3) were repeated using the prepreg preparedin (2) above, to manufacture a cured resin sheet.

The volatile content (Vc) and resin content (Rc) were determined fromthe data measured in the procedure of manufacturing the cured resinsheet from the prepreg. The determined Vc and Rc are set forth in Table2.

EXAMPLE 9

(1) Preparation of Thermosetting Solution Composition

In a four-necked 2,000 mL volume separable flask equipped with astirrer, a reflux condenser and a nitrogen gas inlet were placed 294.22g (1.000 mol) of a-BPDA, 124.12 g (0.500 mol) of PEPA, and 415.06 g ofmethanol in a nitrogen gas stream. The resulting mixture was stirredunder reflux for 5 hours to give a homogeneous solution (the mixtureturned into a homogeneous solution within approx. 3 hours, but thestirring under reflux was continued for additional 2 hours. The solutionwas then cooled to room temperature. To the solution were added understirring 109.63 g (0.375 mol) of TPE-R and 94.62 g (0.875 mol) of PPD.The resulting mixture was heated at 60° C. for 60 minutes to give ahomogeneous solution (thermosetting solution composition). Further, thehomogeneous solution was processed in the same manner as in Example1-(1), to give a clear resin film (thickness: approx. 0.1 mm).

The viscosity of the homogeneous solution and Tg of the resin film areset forth in Table 1.

(2) Preparation of Prepreg

The above-mentioned homogeneous solution (thermosetting solutioncomposition) was spread over a polyethylene terephthalate (PET) film toform a solution film. On the solution film was placed a carbon fibercloth (FAW 320 g/m², plain cloth, T800-12K, available from Toray Corp.)having a size of 320 mm×320 mm. Thus prepared laminate was placed on ahot plate heated to 40° C. under the condition that the PET film wasbrought into contact with the hot plate. On the hot plate, the uppersurface of the carbon fiber cloth was lightly pressed onto the PET filmso that the cloth could be impregnated with the solution. Subsequently,the solution-impregnated carbon cloth was separated from the PET film,and dried by hanging it for 3 minutes in a hot air oven heated to 90° C.The dry carbon cloth was taken out of the oven, placed between a pair ofPET film (thickness: 25 μm), and pressed at a pressure of 0.1 MPa forone minute by means of a hot press heated to 80° C. Thus, a prepreg wasprepared.

Thus prepared prepreg showed good tackiness and drapeability.

The prepreg was subjected to measurement of dynamic viscoelasticity. Themeasured viscoelasticity is shown in FIG. 1.

(3) Manufacture of Cured Resin Sheet

The prepreg was successively heated at 135° C. for 30 min., 180° C. for30 min., 250° C. for 30 min., 300° C. for 30 min., and 370° C. for 60min., to manufacture a cured resin sheet.

The volatile content (Vc) and resin content (Rc) were determined fromthe data measured in the procedure of manufacturing the cured resinsheet from the prepreg. The determined Vc and Rc are set forth in Table2.

EXAMPLE 10

(1) Preparation of Thermosetting Solution Composition

In the same separable flask as that described in Example 9-(1) wereplaced 294.22 g (1.000 mol) of a-BPDA, 124.12 g (0.500 mol) of PEPA,1.25 g of 2-methylimidazole, and 415.06 g of methanol in a nitrogen gasstream. The resulting mixture was stirred under reflux for 3 hours togive a homogeneous solution (the mixture turned into a homogeneoussolution within approx. 1 hour, but the stirring under reflux wascontinued for additional 2 hours. The solution was then cooled to roomtemperature. To the solution were added under stirring 109.63 g (0.375mol) of TPE-R and 94.62 g (0.875 mol) of PPD. The resulting mixture washeated at 60° C. for 60 minutes to give a homogeneous solution(thermosetting solution composition).

The homogeneous solution was subjected to measurement of ¹-NMR spectrum.The ¹H-NMR spectrum is seen in FIG. 2.

Further, the homogeneous solution was processed in the same manner as inExample 1-(1), to give a clear resin film (thickness: approx. 0.1 mm).

The viscosity of the homogeneous solution and Tg of the resin film areset forth in Table 1.

The other physical characteristics of the resin film are set forthbelow:

tensile strength: 127 MPa (at 23° C., according to ASTM D 882)

tensile modulus: 2.8 GPa (at 23° C., according to ASTM D 882)

breaking extension: 13% (at 23° C., according to ASTM D 882)

water absorption: 2.2t (at 23° C., saturation absorption, according toASTM D 570)

thermal decomposition temperature: 563° C.

linear expansion coefficient: 51 ppm

(2) Preparation of Prepreg

The procedures of Example 1-(2) were repeated using the homogeneoussolution prepared in (1) above, to prepare a prepreg.

(3) Manufacture of Cured Resin Sheet

The procedures of Example 1-(3) were repeated using the prepreg preparedin (2) above, to manufacture a cured resin sheet.

The volatile content (Vc) and resin content (Rc) were determined fromthe data measured in the procedure of manufacturing the cured resinsheet from the prepreg. The determined Vc and Rc are set forth in Table2.

EXAMPLE 11

(1) Preparation of Thermosetting Solution Composition

In the same separable flask as that described in Example 9-(1) wereplaced 294.22 g (1.000 mol) of a-BPDA, 124.12 g (0.500 mol) of PEPA,1.25 g of 2-methylimidazole, and 415.06 g of n-propanol in a nitrogengas stream. The resulting mixture was stirred under reflux for 3 hoursto give a homogeneous solution (the mixture turned into a homogeneoussolution within approx. 1 hour, but the stirring under reflux wascontinued for additional 2 hours. The solution was then cooled to roomtemperature. To the solution were added under stirring 109.63 g (0.375mol) of TPE-R and 94.62 g (0.875 mol) of PPD. The resulting mixture washeated at 60° C. for 60 minutes to give a homogeneous solution(thermosetting solution composition). Further, the homogeneous solutionwas processed in the same manner as in Example 1-(1), to give a clearresin film (thickness: approx. 0.1 mm).

The viscosity of the homogeneous solution and Tg of the resin film areset forth in Table 1.

(2) Preparation of Prepreg

The procedures of Example 9-(2) were repeated except that thehomogeneous solution prepared in (1) above was used, and the dryingprocedure was performed at 100° C. for 15 minutes, to prepare a prepreg.

Thus prepared prepreg showed good tackiness and drapeability.

The prepreg was subjected to measurement of dynamic viscoelasticity. Themeasured viscoelasticity is shown in FIG. 1.

(3) Manufacture of Cured Resin Sheet

The procedures of Example 9-(3) were repeated using the prepreg preparedin (2) above, to manufacture a cured resin sheet.

The volatile content (Vc) and resin content (Rc) were determined fromthe data measured in the procedure of manufacturing the cured resinsheet from the prepreg. The determined Vc and Rc are set forth in Table2. TABLE 1 Monomer Solution Tg of cured content(wt. %) viscosity(poise)sheet (° C.) Example 1 66 105 323 Example 2 68 112 365 Example 3 68 107319 Example 4 70 106 321 Example 5 65 107 342 Example 6 71 115 317Example 7 70 110 336 Example 8 60.5 106  *1 Example 9 60 2.0 357 Example10 60 2.2 357 Example 11 60 113 357Remarks: The monomer content means the concentration of the reactivecomponents in the thermosetting solution composition.*1 means that no clear Tg was observed at temperatures below 400° C.

TABLE 2 Homogeneous Vc Rc solution (wt. %) (wt. %) Example 1 16 39Example 2 15 39 Example 3 16 40 Example 4 15 39 Example 5 15 38 Example6 15 39 Example 7 16 39 Example 8 15 39 Example 9 13 41 Example 10 13 41Example 11 14 36

The following examples 12 and 13 describe the preparation of the curedresin article in the manner as illustrated in FIG. 4.

EXAMPLE 12

The prepreg prepared in Example 5-(2) was cut to give 16 prepreg sheets,each having a size of 50 mm×60 mm. The 16 prepreg sheets were laminatedone on another, and thus prepared laminate was placed in theheat-resistant bag (as is illustrated in FIG. 4). The open end of thebag was sealed by heat sealing, and the bag was placed in a hot press.The laminate in the bag was so heated under pressure, under theconditions of the degree of vacuum in the bag and the heatingtemperature that the historical curve in FIGS. 5 to 7 could besatisfied. Thus, a cured resin article was manufactured.

The cured resin article was subjected to measurement of the interlaminarshear strength at 23° C. according to ASTM D2344, to give a shearstrength of 60 MPa. The cured resin article was further subjected todetection of flaw by means of a supersonic flaw detector. No significantflaw was detected.

EXAMPLE 13

The prepreg prepared in Example 9-(2) was cut to give 12 prepreg sheets,each having a size of 300 mm×300 mm. The 12 prepreg sheets werelaminated one on another, and thus prepared laminate was placed in theheat-resistant bag (as is illustrated in FIG. 4). The open end of thebag was sealed by heat sealing, and the bag was placed in a hot press.The laminate in the bag was so heated under pressure, under theconditions of the degree of vacuum in the bag and the heatingtemperature that the historical curve in FIGS. 8 to 10 could besatisfied. Thus, a cured resin article was manufactured.

The cured resin article contained the carbon fiber matrix of 59 vol. %and a void volume of 0.5 vol. %. The carbon fiber matrix content andvoid volume were determined according to ASTM D3171.

Then, the cured resin article was subjected to detection of flaw by meanof a supersonic flaw detector. No significant flaw was detected.

The physical characteristics of the cured resin article are set forthbelow:

Flexural strength (according to AST D790):

-   -   815 MPa (at 23° C.), 479 MPa (at 288° C.)

Flexural modulus (according to ASTM D790):

-   -   61.9 GPa (at 23° C.), 62.0 GPa (at 288° C.)

Interlaminar shear strength (according to ASTM D2344): 68.8 MPa (at 23°C.), 38.2 MPa (at 288° C.)

The cured resin article was further heated at 357° C. for 6 hours in anhot air oven. Thus heated article was subjected to measurement of theinterlaminar shear strength. The results were set forth below:

Interlaminar shear strength (according to ASTM D2344): 49.6 MPa (at 23°C.), 33.9 Ma (at 288° C.)

The following examples 14 and 15 describe the preparation of athermosetting powder composition, the preparation of a thermosettingsolution composition from the powdery composition, the preparation of aprepreg from the prepared thermosetting solution composition, and themanufacture of a cured resin article.

EXAMPLE 14

(1) Preparation of Thermosetting Powder Composition

40.00 g of the homogeneous solution (thermosetting solution composition)prepared in Example 10-(1) was placed in a 500 mL volume eggplant-typeflask. The flask was dipped in a water bath heated to 40° C., and theflask was evacuated for 3 hours by an evaporator to remove methanol.Thus, a powdery composition (thermosetting powder composition) wasprepared.

The powdery composition was examined in the following manner.

A polyimide film having a size of 300 mm×300 mm and a air permeabletetrafluoroethylene/glass sheet having the same size and a thickness of2 mm is placed on a stainless steel plate having the same size in order.On the air permeable sheet was placed a stainless steel frame (width 50mm, length 100 mm, thickness 3 mm). The powder composition was placed inthe frame. On the frame were placed in order the same air permeabletetrafluoroethylene/glass sheet, polyimide film and stainless steelplate so as to cover the frame. The frame with the covering sheets wasplaced in a high temperature vacuum press (KVHC-PRESS, available fromKitagawa Seiki Co., Ltd.) and heated from room temperature to 250° C.for 3 hours and further at 250° C. for 2 hours. The vacuum press wasevacuated to make the inner space a vacuum of 2 Torr for 30 minutes.Thereafter, the powdery composition in the frame was heated to 370° C.for 24 mites under 5 MPa, and kept under the condition for one hour. Thecomposition was then cooled in vacuum to 30° C. under pressure, to givea resin plate (width 50 mm, length 100 mm, thickness 3 mm).

The resin plate was cut to a piece of 50 mm×50 mm, and subjected to thefollowing measurement of heat loss.

Weight loss after heat treating:

-   -   0.60% (300° C. 500 hours, in air)    -   0.15% (275° C., 500 hours, in air)

EXAMPLE 15

(1) Preparation of Thermosetting Powder Composition

20.00 g of the homogeneous solution (thermosetting solution composition)prepared in Example 10-(1) was placed in a 300 mL volume eggplant-typeflask. The flask was dipped in a water bath heated to 40° C., and theflask was evacuated for 3 hours by an evaporator to remove methanol.Thus, 14.2 g of a powdery composition (thermosetting powder composition)was prepared.

The homogeneous solution was subjected to measurement of ¹H-NMRspectrum. The ¹H-NMR spectrum is seen in FIG. 3.

(2) Preparation of Thermosetting Solution Composition from ThermosettingPowder Composition

In 4.59 g of ethanol as dissolved 13.78 g of the powdery composition(thermosetting powder composition) obtained in (1) above, to give ahomogeneous solution (thermosetting solution composition).

(3) Preparation of Prepreg

A prepreg was prepared in the manner as described in Example 1-(2) usingthe ethanolic solution composition prepared in (2) above.

Thus prepared prepreg showed good tackiness and drapeability.

The prepreg was subjected to measurement of dynamic viscoelasticity. Themeasured viscoelasticity is shown in FIG. 1.

(4) Manufacture of Cured Resin Sheet

The procedures of Example 1-(3) were repeated using the prepreg preparedin (3) above, to manufacture a cured resin sheet.

The volatile content (Vc) and resin content (Rc) were determined fromthe data measured in the procedure of manufacturing the cured resinsheet from the prepreg. It was determined that Vc was 15% and Rc was41%.

(5) Concentration Dependency and Temperature Dependency of SolutionViscosity of Thermosetting Solution Composition

The thermosetting powder composition prepared in Example 14-(1) wasdissolved in ethanol to give homogeneous solutions having differentconcentrations. The relationship between the concentration of thesolution and the solution viscosity is set forth below. ConcentrationSolution viscosity Imide content of powder(wt. %) (30° C., poise) (wt.%) 50 0.3 40 62.5 1.9 50 75 54 60Remarks: The imide content was determined by the following method: Thepowdery composition (thermosetting powder composition) was processed togive a fully imidized product which was then heated at 250° C. for 30minutes to completely remove methanol; the weight of the imidizedproduct was measured, and a ratio of weight loss from the powdercomposition to the imidized product was calculated. The imide contentwas calculated by the following equation:Imide content (%)=Concentration of powder (%)×(1−ratio of weight loss)

The thermosetting solution composition (concentration of 62.5 wt. % inethanol) prepared from the thermosetting powder composition in Example14-(1) was subjected to measurement of temperature dependency ofsolution viscosity. The results are set forth below. Temperature (° C.)Solution viscosity (poise, 30° C.) 20 4.5 30 1.9 40 1.0 50 0.6

COMPARISON EXAMPLE 1

The procedures of Example 1-(1) were repeated except for replacinga-BPDA (0.0400 mol) with s-BPDA (11.77 g, 0.0400 mol), to prepare ahomogeneous solution. A portion of the homogeneous solution was spreadon a polyimide film in the same manner as in Example 1-(1) and heated at80° C. for 30 min., 135° C. for 30 min., 180° C. for 30 min., 250° C.for 30 min., 300° C. for 30 min., and 370° C. for 60 min. In the courseof the heating, the solution film turned into an opaque and brittlefilm.

1. A thermosetting solution composition comprising abiphenyltetracarboxylic acid compound containing at least 15 mol % of apartial lower aliphatic alkyl ester of 2,3,3′,4′-biphenyltetracarboxylicacid and/or a partial lower aliphatic alkyl ester of2,2′,3,3′-biphenyltetracarboxylic acid, an aromatic diamine compound ina molar amount larger than a molar amount of the biphenyltetracarboxylicacid compound, a partial lower aliphatic alkyl ester of4-(2-phenylethynyl)phthalic acid compound in a molar amount as much as1.8-2.2 times a molar amount corresponding to a difference between themolar amount of the aromatic diamine compound and the molar amount ofthe biphenyltetracarboxylic acid compound, and an organic solventcomprising a lower aliphatic alcohol.
 2. The thermosetting solutioncomposition of claim 1, wherein the lower aliphatic alcohol is methanolor ethanol.
 3. The thermosetting solution composition of claim 1,wherein each of the partial lower aliphatic alkyl esters is a partialmethyl ester or a partial ethyl ester.
 4. The thermosetting solutioncomposition of claim 1, wherein the molar amount of the partial loweraliphatic alkyl ester of 4-(2-phenylethynyl)phthalic acid compound is asmuch as 1.95-2.05 times a molar amount corresponding to the differencethe molar amount of the aromatic diamine compound and the molar amountof the biphenyltetracarboxylic acid compound.
 5. The thermosettingsolution composition of claim 1, wherein a total amount of thebiphenyltetracarboxylic acid compound, the aromatic diamine compound,and 2-(2-phenylethynyl)phthalic acid compound is in the range of 30 to80 wt. %, per the amount of the solution composition.
 6. Thethermosetting solution composition of claim 1, wherein thebiphenyltetracarboxylic acid compound comprises at least 50 molar % of2,3,3′,4′-biphenyltetracarboxylic acid compound comprising a partiallower aliphatic alkyl ester of 2,3,3′,4′-biphenyltetracarboxylic acidcompound.
 7. The thermosetting solution composition of claim 1, whereinthe aromatic diamine compound comprises at least 50 molar % of anaromatic diamine having one aromatic ring in a molecular structurethereof.
 8. The thermosetting solution composition of claim 1, whereinthe aromatic diamine compound comprises p-phenylenediamine,1,3-bis(4-aminophenoxy)enzene, or a mixture thereof.
 9. Thethermosetting solution composition of claim 1, which further comprisesan imidazole compound.
 10. A thermosetting solution compositioncomprising a biphenyltetracarboxylic acid contend containing at least 15mol % of a partial methyl ester of 2,3,3′,4′-biphenyltetracarboxylicacid and/or a partial methyl ester of 2,2′,3,3′-biphenyltetracarboxylicacid, an aromatic diamine compound in a molar amount larger than a molaramount of the biphenyltetracarboxylic acid compound, a partial methylester of 4-(2-phenylethynyl)-phthalic acid compound in a molar amount asmuch as 1.8-2.2 times a molar amount corresponding to a differencebetween the molar amount of the aromatic diamine compound and the molaramount of the biphenyltetracarboxylic acid compound, and an organicsolvent comprising ethanol.
 11. A thermosetting powder compositioncomprising a biphenyltetracarboxylic acid compound containing at least15 mol % of a partial lower aliphatic alkyl ester of2,3,3′,4′-biphenyltetracarboxylic acid and/or a partial lower aliphaticalkyl ester of 2,2′,3,3′-biphenyltetracarboxylic acid, an aromaticdiamine compound in a molar amount larger than a molar amount of thebiphenyltetracarboxylic acid compound, and a partial lower aliphaticalkyl ester of 4-(2-phenylethynyl)phthalic acid compound in a molaramount as much as 1.8-2.2 times a molar amount corresponding to adifference between the molar amount of the aromatic diamine compound andthe molar amount of the biphenyltetracarboxylic acid compound.
 12. Thethermosetting powder composition of claim 11, wherein each of thepartial lower aliphatic alkyl ester is a partial methyl ester.
 13. Aprepreg comprising a sheet matrix of a reinforcing fiber impregnatedwith the thermosetting solution composition of claim
 1. 14. A prepregcomprising a sheet matrix of a reinforcing fiber impregnated with thethermosetting solution composition of claim
 10. 15. A method ofmanufacturing a resin article which comprises laminating a plural numberof the prepregs defined in claim 13 one on another and heating theresulting laminate under pressure.
 16. A method of manufacturing a resinarticle which comprises laminating a plural number of the prepregsdefined in claim 14 one on another and heating the resulting laminateunder pressure.